.png){kind=small}
.png){kind=small}
BackTable / ENT / Article
Evaluation & Diagnosis of Congenital Hearing Loss
Iman Iqbal • Updated Aug 31, 2024 • 62 hits
Congenital hearing loss affects a significant number of newborns, presenting a critical need for early detection and intervention. Infants diagnosed with hearing loss shortly after birth typically undergo a series of hearing screenings, which utilize Otoacoustic Emissions (OAE) and Auditory Brainstem Response (ABR) tests. However, the journey doesn't end with initial detection; hearing loss can emerge later in childhood, underscoring the need for continuous monitoring.
While early detection is key, the complexity of managing congenital hearing loss lies in the nuanced decisions regarding further diagnostic testing, imaging, and potential interventions. The decision-making process, influenced by the degree and type of hearing loss, as well as individual patient factors, often involves balancing the benefits of immediate action with the potential risks of procedures.
This article, featuring excerpts from the BackTable ENT Podcast, discusses the intricacies of diagnosing and managing congenital hearing loss, as explained by otolaryngologists Dr. Rachel St. John and Dr. Walter Kutz. You can listen to the full podcast below.
The BackTable ENT Brief
• Infants with congenital hearing loss are typically diagnosed through initial audiological tests like behavioral audiograms and ABR tests by three to four months of age.
• Newborn hearing screening, utilizing OAE and automated ABR, is essential for early detection, particularly in high-risk infants from the NICU.
• In the U.S., most states require newborn hearing screenings before hospital discharge, with additional protocols for babies born outside traditional hospital settings.
• Monitoring for late-onset hearing loss is crucial, as it can emerge later in childhood and may require specialized care, including cochlear implants.
• Factors such as prematurity, ICU stays, and prenatal infections (e.g., TORCH, CMV) are critical in assessing potential hearing loss, highlighting the need for thorough birth history evaluations.
• For mild to moderate bilateral hearing loss, genetic testing often precedes imaging, especially in cases where the likelihood of structural abnormalities is low.
• The severity and nature of hearing loss influence imaging choices, with MRI preferred for profound or asymmetric sensorineural loss and CT for assessing structural abnormalities in mixed hearing loss.
Table of Contents
(1) Detecting Pediatric Hearing Loss: Newborn Screening Protocols
(2) The Role of Birth History & ABR in Diagnosing Congenital Hearing Loss
(3) How Severity & Asymmetry of Hearing Loss Influence the Diagnostic Workup
(4) Choosing the Right Imaging Modality for Mixed Hearing Loss: CT vs MRI
Detecting Pediatric Hearing Loss: Newborn Screening Protocols
Infants with congenital hearing loss typically present to the clinic at around three to four months old after completing initial audiological assessments, such as a behavioral audiogram or auditory brainstem response test. These diagnostic measures confirm whether the child is deaf or hard of hearing. In addition to these infants, older children who may develop late-onset hearing loss may also present to clinic, highlighting the importance of ongoing monitoring beyond the newborn period, as hearing loss can emerge later in childhood.
Newborn hearing screenings are crucial for early detection and involve two primary methods: otoacoustic emissions and automated ABR. OAE is widely used in well-baby nurseries and measures the cochlea's response to sound, while automated ABR assesses the entire hearing pathway, including the brainstem. For infants in the Neonatal Intensive Care Unit (NICU), who are at higher risk for conditions like auditory neuropathy, the automated ABR is preferred because it can detect issues that OAE might miss. The recommended timeline for hearing screening is screening by one month, diagnostic evaluation by three months for those who don't pass, and implementing necessary services by six months.
In the United States, most states mandate newborn hearing screenings before hospital discharge, but babies born outside hospitals, such as at birthing centers or at home, might not receive this screening. Legislation in states like Texas now requires these babies to be referred for screening even if they weren't born in a traditional hospital setting. Late-onset hearing loss can occur at any age, from infancy through adulthood, and may even be associated with conditions like acoustic neuromas. These cases often require specialized care, and patients are typically referred by pediatricians or otolaryngologists for further evaluation and treatment, which may include interventions like cochlear implants.
[Dr. Rachel St. John]
I'll go first. For me, it's a little predetermined because in order to get into my clinic, you have to have some diagnostic measure of being deaf or hard of hearing, either a behavioral audiogram or an ABR. By the time I see children, they've gone through the audiology process. The parents have at least gotten that initial information that their child is deaf or hard of hearing. If they come to me as infants, it's probably going to be, I'll usually see them around month three or four after they've been through all the diagnostic process and arrive in my clinic. Then, because late onset hearing changes are so much more prevalent than congenital, we get lots and lots of older children, toddlers, school age, teenagers who present in our clinic as well.
[Dr. Gopi Shah]
Before we move on, I just wanted to touch on the screening that leads them to get that hearing loss detected. I know, Dr. St. John, I remember you talking about this when I was a resident and just the importance of making sure we're catching kids at a certain timeline. Can you remind me about what that timeline is? I know, there's the newborn hearing screen that happens in the hospital. What happens after that? Can you have kids who pass that, who ultimately actually do end up seeing you for hearing loss? If you fail that, then what happens?
[Dr. Rachel St. John]
Absolutely. That's a lot. Yes, but I'm going to go through it very succinctly, and then maybe Walt can chime in with this too. Very briefly, there's two different kinds of newborn hearing screening that we use. OAE, which are otoacoustic emissions, and automated ABR, that's an automated acoustic brainstem response. The real quick and dirty on the two of them is that they both-- The thing to remember is they're both screens, they're not diagnostic.
When you do an OAE, which is used fairly widely in the newborn nursery, the well baby nursery, you're basically putting a probe in the ear and emitting a sound and looking for the cochlea to actually make its own microphonic response. A cochlea that is processing sound makes its own sound and that gets picked up by the transducer. There's no interpretation. The machine either picks that up or doesn't, and it spits out pass or refer for more testing.
For kids who have been in the NICU, they are more likely to have something called auditory neuropathy, which I am sure you're going to ask us about later in this podcast. Those kids can actually get through an OAE. They can actually have a typical looking OAE and not be hearing typically. For those kids, it's much more common to use an automated ABR. That's actually checking the entire hearing pathway from an external ear through the middle ear, inner ear, cochlear nerve, all the way to the brainstem. It's looking for a brainstem response in response to a sound. If you have auditory neuropathy, that will get picked up and that will come out as a fail or not passed.
In terms of timeline, the standard timeline for kids just born, without other complication, the American Academy of Pediatrics refers to it as the 136 model. It's screening by one month of age. Then for infants who don't pass that screening, you want a diagnostic with a pediatric audiologist by three months of age. Then for those children who are identified as deaf or hard of hearing, you want to make sure that services are implemented by six months of age. That's the timeline for screening.
There's a lot of kids, a lot, who do pass that newborn hearing screening and then have hearing loss late onset. The place that those kids ideally are supposed to be identified is in the medical home with those pediatric visits. Really, it's very insidious. If it happens during the toddler years, you're basically looking for language development and kids and parental concern that kids are not responding the way that you would expect them. Those would be things that would prompt you to do another hearing evaluation.
[Dr. Ashley Agan]
In terms of the newborn hearing screen, is it true that in the state of Texas, if you're born in a hospital, you should have had a newborn hearing screen prior to leaving, whether it's a healthy baby nursery or the neonatal ICU?
[Dr. Rachel St. John]
It's actually true in most states. The vast majority of states have legislation for newborn hearing screening. That's either a legal mandate through law or that's policy. There's very few states at this point. I would have to go to the CDC Early Hearing Detection Intervention website has all that data in terms of who's got current legislation in place, but it's most of the 50 states that do.
[Dr. Ashley Agan]
I always ask, and I'm sure everybody does, as part of my birth history, because we do have a small percentage or group of babies that are either born at a birthing center or home where the hearing screen is not done and maybe you're seeing them. For us we'll see them for laryngomalacia at two months and yet here we are without a history of a hearing screen. Just things to keep in mind.
[Dr. Rachel St. John]
Interestingly, Texas a couple of years ago passed legislation that now requires both children's hospitals and birthing centers to at least refer those children to a screening site. It used to be those babies that were born at those sites were exempt, for lack of a better word, and they could easily fall through the cracks. At least in the state of Texas, we have legislation in place now. With midwives as well, if you aren't doing the screening, you can't just say, well, I don't screen. You actually have to make a referral to a place that will.
[Dr. Ashley Agan]
It sounds like these babies will present as early as between three to six months to you, to as late as-- When you say late onset, are you talking like 6 months, 18 months, 3-year-old, 10-year-old?
[Dr. Rachel St. John]
Yes. All of the above. In all of the above. It can happen for so many. I'm sure Walter has seen quite a few patients, presenting, they'll have like a late onset acoustic neuroma. That could happen anytime. That could happen in adulthood. That could happen in your late teens. The timeline is life, basically.
[Dr. Ashley Agan]
Dr. Kutz, how do these patients present to your clinic? Is it similar or is it different?
[Dr. Walter Kutz]
Being a tertiary, I'm sorry, I guess being a subspecialist in a tertiary hospital, generally speaking, they're going to be referred in by an otolaryngologist, sometimes audiologist. Typically the pediatricians sending one of the patients to our practice, they'll see one of our pediatric otolaryngologists first. Oftentimes, I'll see the patients once it's been determined they need something like a cochlear implant, or maybe they have atresia and they're considering an atresia plaster or bone-anchored hearing aid. That's typically when I would see patients with hearing loss.
Listen to the Full Podcast
Stay Up To Date
Follow:
Subscribe:
Sign Up:
The Role of Birth History & ABR in Diagnosing Congenital Hearing Loss
When assessing the birth and prenatal history of infants for potential hearing loss, it's essential to consider factors such as prematurity, ICU stays, and perinatal infections. Prenatal care is also critical, especially in identifying TORCH infections, CMV, and syphilis, which can contribute to hearing loss. Additionally, late-onset hearing loss may be linked to noise exposure, such as frequent use of earphones or participation in loud activities like hunting or going to concerts, highlighting the importance of asking about environmental factors.
After diagnosis, the next step involves confirming the diagnosis with an ABR test. The ABR requires the infant to remain still, which can be achieved either through natural sleep or sedation. While napping ABRs are preferred in order to avoid sedation, the quality of sleep and the child's cooperation are critical in obtaining accurate results. In some cases, if the child does not sleep soundly or is resistant, a sedated ABR may be necessary. In situations where the child has conditions like otitis media, the ABR might need to be conducted in conjunction with procedures like tube placement. The quality of the ABR results is crucial, especially when considering advanced treatments like cochlear implants.
[Dr. Ashley Agan]
In terms of birth history, prenatal history, I go through how many weeks was the baby born at, ICU stay, any perinatal infections. What other questions in history do you feel like, hey, this is important, but maybe something that we don't always think about that you always make sure you ask every time?
[Dr. Rachel St. John]
That's a good question. I think you covered a lot of them. Prematurity and all of the things that go along with prematurity, there's a ton of risk factors there for hearing changes. Certainly, I think prenatal care is a really big one too, because those moms are going to get testing for TORCH infections and potentially CMV, syphilis, those kinds of things. I think one of the things that I have seen, I think it's just through practice and I've seen enough of these kids, it's not super common, but it happens enough that I've changed my practice, is with kids who have later onset hearing changes. I'm starting to ask much more routinely about noise exposure, both from-- Because, we're sort of in ear pod generation with these kids, they are spending a lot of the day with headphones or earbuds in and are not always mindful of volume.
Also, we're here in Texas, I have a fair number of families and one of the sort of cultural activities that they participate in very regularly is hunting. I have several kids in my practice who have had acoustic trauma and that sort of classic 2,000 hertz drop, because it's just not been the culture of the family to wear ear protection. The kid I saw most recently was really upset, he thought he had done something wrong and he started crying and he said, but Papa doesn't wear it either. We have headphones, but they're always in the truck. Obviously I had to convince him that no, he was fine. Everybody has to wear them, not just him, he's not in trouble. I am much more aggressive about screening for that when I am talking with families.
[Dr. Ashley Agan]
Yes, it's definitely important. When we've had these newborns who are coming in and diagnosed with some congenital hearing loss, what happens next? What's the next step of the workup? Do they need a sedated ABR or a natural sleeping ABR to really confirm. Do you have a preference for that?
[Dr. Rachel St. John]
Yes, I think in terms of the ABR, basically a good quality ABR requires a still person. We can actually do napping ABRs in older people too, if they're cooperative. I think in terms of preference between napping and sedated, I think Dr. Kutz will speak to this as well, but my preference for the child is always if we can get it napping, great. For infants who are poor nappers, even if they do sleep, sometimes the quality of the sleep is fairly light and then you don't get a great ABR.
I think it's whatever gets you the best information. If we have a kid that you sleep deprive and you give them a bottle and they just conk out and they're a great sleeper, you're probably going to get a good quality ABR. Then there's some kids who just fight that eternally and you might end up needing a sedated ABR to get a decent evaluation on them.
[Dr. Walter Kutz]
Yes, I agree with that. I also really listen to the audiologist, I think they're-- Especially for ABR and oftentimes when I'm seeing the child, we're talking about a cochlear implant and it's very important to establish hearing. Oftentimes these kids will have otitis media, so they may need tubes anyway to get a really accurate ABR. We may take them to the operating room, place tubes and then obtain an ABR. The thing is an ABR takes 30-45 minutes in the operating room. There's some concern with children being under anesthesia for a long length of time. I do agree with Dr. St. John, trying to get a napping ABR is definitely preferable. I think we definitely want to have good information if we're going to progress to a cochlear implant.
How Severity & Asymmetry of Hearing Loss Influence the Diagnostic Workup
The degree of hearing loss in a child can influence the approach to their diagnostic workup, but the overall process remains consistent whether the loss is unilateral or bilateral. For infants with profound hearing loss who are potential candidates for cochlear implants, imaging, such as MRI, becomes an essential part of the evaluation process. However, for those with mild to moderate hearing loss, especially if it is bilateral and symmetrical, imaging may not be immediately necessary. In such cases, comprehensive genetic testing often takes precedence, particularly since a significant portion of congenital hearing loss is genetic and may not involve structural abnormalities that would be detected on imaging. For example, conditions like connexin 26-related hearing loss are typically not associated with visible changes on MRI, so imaging might be skipped if genetic testing confirms this diagnosis.
On the other hand, when hearing loss is asymmetric or mixed in nature, imaging becomes more critical. Asymmetry in hearing loss may indicate underlying structural issues, such as an absent cochlear nerve or more rare conditions like a glioblastoma along the auditory pathway, which, though uncommon, must be ruled out. Additionally, mixed hearing loss might suggest conditions like an enlarged vestibular aqueduct, where imaging could help clarify the diagnosis and guide management. Ultimately, the approach to workup varies depending on the individual patient’s presentation and the degree of hearing loss.
[Dr. Gopi Shah]
Are you less aggressive with mild bilateral or mild unilateral than you would be in moderate or profound bilateral?
[Dr. Rachel St. John]
This is interesting. I'm going to be interested to see what Walter says, because I don't, I feel like some of this is based on the patient population you see. For me, in general, I do the same thing, same kind of algorithm for unilateral and bilateral. I think in terms of being aggressive, the timeline might change. For example, if we have somebody who gets an ABR and there's no response and they're a cochlear implant candidate, we're going to really make sure that imaging is part of that. Because we've got anywhere from 6 months to 12 months until the time of implant. Imaging is going to be a really important part of that.
Whereas if I have a baby who is mild to moderate, imaging is probably going to be part of that process, but I'm not necessarily going to feel the need to get a sedated MRI of the internal auditory canals right away, unless it's going to change management. Because I tend to default to genetic testing first in kids who have bilateral sensorineural. The latest data from CDC shows that that's 50 to 60% of babies who are born deaf or hard of hearing, it's going to be genetic because it's often non-syndromic and autosomal recessive. You might not see any family history, even though it's part of the thing that we ask about.
I'm going to go to comprehensive genetic testing first, because that might obviate the need for anything else. If I find out it's connexin 26 and that kid is going to do very well with bilateral hearing aids. I'm not going to image them because that's a gap junction issue, that's a histopathology issue. That's not structural. I would fully expect to see a typical MRI. I think the order in which you do them and the timeline in which you do them changes for me, depending on the degree. Ultimately I'm going to address the same things.
I'm interested to hear what Walt says, because I see patients on a little bit different timeline and in a little different span than he does, so that might change depending on who you're working with.
[Dr. Walter Kutz]
I follow pretty similar decision-making, and every patient's different, right? Some may be premature. They may have family history. I do agree if they have an abnormal connexin test, they're unlikely going to have an abnormal MRI. Of course, if they have severe or profound hearing loss, you're going to do a cochlear implant and you're going to want to do some imaging for preoperative planning. If a child has symmetric, mild to moderate sensory hearing loss, I don't think they necessarily need imaging. I think if there's asymmetric hearing loss that's significant, that's when I would definitely lean towards imaging.
I do agree, in most cases if they have to have abnormality, it's going to be something like-- You're not going to see anything on imaging or they may have an absent cochlear nerve on one side. I do recall a recent case of I think a 12-year-old or 13-year-old that had some asymmetric hearing, retained an MRI and actually had a glioblastoma along the auditory pathway, which is very, very rare. You don't want to base all your decisions off of one case, but we did order the MRI because of the asymmetry of the hearing loss. I think mild to moderate, symmetric, child's doing okay with hearing aids, I probably wouldn't image them, but to carefully follow their hearing.
[Dr. Rachel St. John]
Yes. I think the asymmetry piece is really big. That's something that I always talk about with residents when I'm teaching is, especially if it's late onset, but regardless, it's like, if you've got an asymmetric presentation, you do think more structural and you want to rule out the bad stuff. Especially, and I think this is something you guys are going to get to, but if you have a mixed presentation, one of the things that always starts percolating in my mind is enlarged vestibular aqueduct, because we see a fair amount of it. I think the point about asymmetry is pretty critical to keep in mind.
Choosing the Right Imaging Modality for Mixed Hearing Loss: CT vs MRI
Evaluating mixed hearing loss requires an additional diagnostic step in deciding between CT vs. MRI for imaging. The choice often depends on the specific clinical context and what the imaging is expected to reveal. Generally, CT scans are preferred for assessing the temporal bone and identifying structural abnormalities like an enlarged vestibular aqueduct or ossicular anomalies. CT scans are quick and provide detailed bone anatomy, making them useful for mixed hearing loss cases. However, they do involve a significant amount of radiation, which can be a concern, particularly for very young children.
MRI, on the other hand, is better suited for evaluating the cochlear nerve and identifying inner ear abnormalities, especially in cases of asymmetric hearing loss where there might be a concern for conditions like tumors. Although MRI provides valuable information, it is a lengthier procedure that typically requires sedation in young children, making it less desirable for routine follow-ups unless the findings will directly impact management.
Thus, for most cases of mixed hearing loss, unless there is a specific, immediate concern like tumor or progressive hearing loss that could alter management, imaging can often be delayed until the child is older and can undergo a CT scan without sedation. Regular follow-ups are crucial to ensure that any changes in hearing status are monitored and that imaging is performed when necessary.
[Dr. Ashley Agan]
Speaking of mixed, and I feel like I asked you this, Rachel, all the time in the clinic when I have like a mixed result, do you like MRI? Do you like CT? How do you decide which scan to get? To me, my rule of thumb is sensorineural, I tend to get MRI just because you see the nerve better. Asymmetry, I like MRI because of sensorineural, make sure there's no tumor, conduct a temporal bone, better bone anatomy and a CT. For mixed, I'm never quite sure which one to get.
[Dr. Rachel St. John]
I call Dr. Kutz and I'm like, "What would you do?" This is where I would really punt to the otologists, although I think I've read a lot of different things in the literature. I've read that CT is adequate for evaluating EVAS, and then MRI is superior for evaluating EVAS. Then I've talked to people who said, I prefer CT or I prefer MRI, and I feel like it's shown up on both studies. I'd love to hear sort of the otology take on that.
[Dr. Walter Kutz]
I think probably the way-- Typically on mixed loss, I think I'd lean towards a CT temporal bone. You're going to most likely see EVA, you can measure the aqueduct pretty easily and see the posterior canal. There's different ways of determining if it's truly an enlarged visceral aqueduct. Then, if you're going to look at acicular abnormalities, you can see the shape of the cochlea. You're not getting MRI. MRI is beneficial if you look at the cochlear nerve status, you know is it hypoplastic or absent, you're looking at inner ear abnormalities, but you can see that on CT scan.
The disadvantage of a CT scan, of course, is there's going to be some radiation involved and it's not negligible with a CT temporal bone. There's a fair amount of radiation. Again, if it's asymmetric or single-sided mixed hearing loss, the kid's doing okay, you can do that CT scan. We don't have to sedate them, or when they're older, to get them out of that young age where the CT scan and the radiation may have more problems in the future. I think I would lean toward a CT scan for mixed hearing loss in most cases.
…
If it's unilateral, I'm not really worried about anything that's going to harm them. I'm not worried about a tumor or anything of that sort. I think you could wait as long as you-- Until you have to have sedation. A CT scan takes about a minute or two. It's pretty quick. Unlike an MRI where it's 30 minutes plus, and then they have to probably be under anesthesia until maybe, three, four, five years of age, depending on the child, maybe even older. You can also get atresia, the same sort of thing. I think atresia is going to cause hearing loss, is going to present with hearing loss and need imaging.
I wouldn't image them necessarily when they're very young. I'd wait till they're probably three or four years of age, they get a CT scan. I don't think you need sedation so fast for most kids, and you're just rolling out a cholesteatoma at that point anyway. That's my thought. If I'm worried about something, if I'm that they have surgery for a cochlear implant, or if I'm worried about something that's going to harm them, then I think you need to push the imaging up. Otherwise, I think you can wait and just check that box at some point and make sure you have the diagnosis.
[Dr. Rachel St. John]
I always tend to go with things that are going to change my management. I talk about that with families too, so that they know what to expect, because, sometimes we have families who just want to know. Then when we talk about the fact that we're not necessarily going to do anything with that information, they actually feel a little differently about waiting a little bit until that child is older and either can handle sedation better or potentially not need it.
I always let them know that should something change, that's something that-- If I have a child who has had, he was born unilateral and then the other ear becomes involved, I'm probably going to want to image that child. If they have really significant progressive, is there-- Because EVAS doesn't have to present as a mix. I've seen it present as predominantly sensorineural. If there is something there that we might do something differently about, I will always push imaging. I think it's important to look at that and say, am I getting this because I want to feel better having gotten it or the family does, or am I actually going to do something with that information?
…
Depending on the family. I tend to follow patients annually, minimum. Then if things are shifting, or if we end up with some transitional challenge, like we're changing, we're entering public school or we're shifting from elementary to junior high and the format for learning changes dramatically. If parents are really anxious, sometimes I'll do something sooner. I just base it on what the family needs.
Podcast Contributors
Dr. Rachel St. John
Dr. Rachel St. John is a practicing ENT and Associate Professor of Clinical Medicine at Children's Medical Center Dallas/UTSW Department of Otolaryngology.
Dr. Joe Walter Kutz
Dr. Joe Walter Kutz is a neurotologist and Professor of Otolaryngology and Neurosurgery at the University of Texas Southwestern Medical Center in Dallas, TX.
Dr. Gopi Shah
Dr. Gopi Shah is a pediatric otolaryngologist and the co-host of BackTable ENT.
Dr. Ashley Agan
Dr. Ashley Agan is an otolaryngologist in Dallas, TX.
Cite This Podcast
BackTable, LLC (Producer). (2021, February 16). Ep. 16 – Congenital Hearing Loss [Audio podcast]. Retrieved from https://www.backtable.com
Disclaimer: The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.
Podcasts
Articles
Pathway to Cochlear Implants for Congenital Hearing Loss
Complex Causes of Pediatric Hearing Loss: Auditory Neuropathy, CMV & Bacterial Meningitis
No OR Time, No Problem: In-Office Pediatric Ear Tube Placement with the Tula System
How to Integrate In-Office Ear Tube Placement into Your Pediatric ENT Practice